package com.lyz.dataStructure.JianZhiOffer;/**
 * @Author:759057893@qq.com Lyz
 * @Date: ${Date} 20:45
 * @Description:
 **/

import java.util.Arrays;
import java.util.Scanner;

/**
 *@Author:759057893@qq.com Lyz
 *@Date: 2019/6/18 20:45
 *@Description:
 **/

/*
一只青蛙一次可以跳上1级台阶，也可以跳上2级……它也可以跳上n级。求该青蛙跳上一个n级的台阶总共有多少种跳法。
 */

public class Test10 {
    public static int JumpFloorII(int target) {
        int one = 1;
        int two = 2;


        if(target<0) return  -1;
        if(target ==1) return 1;
        for(int i =2;i<=target;i++){
            two = 2*one;
            one = two ;
        }
        return one;
    }
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int num =  JumpFloorII( n);
        System.out.println(num);
    }
}
